1. Field of the Invention
The present invention relates to a decorative stainless steel rolled sheet having an embossed pattern and a method of manufacturing the same. More particularly, the present invention relates to a decorative stainless steel rolled sheet having an embossed pattern, which comprises a continuous thin stainless steel sheet subjected to surface treatment such as nanoceramic coating or PVD (Physical Vapor Deposition) ionic coating and a release sheet alone or with a nonwoven fabric layer bonded to one side of the thin stainless steel sheet by means of a hot melt adhesive layer, which are embossed together, and to a method of manufacturing the same.
2. Description of the Related Art
Generally decorative sheets have been utilized as surface finishes for a variety of products that protect the products and impart the outer appearance thereof with various colors, patterns and textures.
For example, decorative sheets are widely employed as interior surface finishes in buildings, elevators, automobiles, ships and airplanes, or as surface finishes for a variety of pieces of furniture or electronic products.
Depending on the end use, the types of decorative sheets are the overlay type, wrapping type, membrane type, and edge type. Overlay type decorative sheets are generally used on the flat top of furniture, MDF (Medium Density Fiberboard) or particle board, and wrapping type decorative sheets are used on portions requiring curved processing such as a narrow chassis or molding.
Also, membrane type decorative sheets are applied to typical furniture having many curved portions or doors, and edge type decorative sheets are applied to corners of furniture or tables or lateral sides of upper sheets thereof. Recently, iron plate type decorative sheets are applied on the outer surfaces of electronic products or other iron plates.
Because conventional decorative sheets are mainly made of a synthetic resin, surface strength and wear resistance are low which undesirably leads to scratching. Also, even when such conventional decorative sheets are subjected to fire-proofing surface treatment, they have low heat resistance and fire resistance and have a weak resistance to fire.
In order to impart decorative sheets with a metal texture, attempts to attach a metal foil to the bottom or top of a base sheet are being made these days.
Although methods of attaching a metal foil may impart the decorative sheet with a metal texture, they are problematic because it is difficult to form various designs including letters or figures on the metal foil provided in the form of a thin film, and also because flexibility may decrease and wrinkling may occur, making it difficult to manufacture the decorative sheet into a rolled sheet and to package and handle it.
Furthermore, when the decorative sheet is attached to a target, it may come off due to not being very flexible and wrinkling.
In particular, it is difficult to apply such a decorative sheet to recessed portions, protruding portions and curved portions of the target because it is not very flexible and because of wrinkling.
Korean Patent No. 0896623 discloses a metal textured decorative sheet and a method of manufacturing the same. Specifically, in the metal textured decorative sheet comprising a base sheet, a metal texture layer formed on the base sheet, a printing layer formed on the metal texture layer, and a transparent film formed on the printing layer, the metal texture layer which includes letters or figures is formed by printing metal ink containing metal particles on the base sheet, the metal ink comprising a dispersion of metal particles having a size of 1˜100 nm, a binder, a solvent and a dispersant. As such, the metal ink may comprise, based on the total weight of the metal ink, 5.0˜50.0 parts by weight of the metal particles, 10.0˜60.0 parts by weight of the binder, 10.0˜40.0 parts by weight of the solvent, and 0.05˜5.0 parts by weight of the dispersant, in which the dispersant may be an alkylamine having a C4˜12 alkyl group, an amide carboxylate, an aminocarboxylate or sodium citrate. Furthermore, the method of manufacturing the metal textured decorative sheet includes forming the metal texture layer on the base sheet thus obtaining a semi-finished product, layering the transparent film having the printing layer on the semi-finished product and then passing the semi-finished product through an emboss roll so as to be hot pressed thus manufacturing a desired sheet, in which the metal texture layer includes letters or figures formed by printing metal ink containing metal particles on the base sheet, the metal ink comprising a dispersion of metal particles having a size of 1˜100 nm, a binder, a solvent and a dispersant. As such, the metal ink may comprise, based on the total weight of the metal ink, 5.0˜50.0 parts by weight of the metal particles, 10.0˜60.0 parts by weight of the binder, 10.0˜40.0 parts by weight of the solvent, and 0.05˜5.0 parts by weight of the dispersant, in which the dispersant may be an alkylamine having a C4˜12 alkyl group, an amide carboxylate, an aminocarboxylate or sodium citrate.
The decorative sheet thus manufactured is advantageous because the metal texture layer is formed by printing the metal ink, thus embodying designs of various metal textures and ensuring flexibility, compared to a metal texture layer in metal foil form. However, this decorative sheet is disadvantageous because the transparent film which constitutes the uppermost part of the decorative sheet is made of a synthetic resin, and thus wear resistance becomes poor, and also because of low resistance to heat and fire, and thus the decorative sheet is weak to fire and may contaminate the environment when it is disposed of.
Moreover, such a decorative sheet is manufactured using a unit for producing the semi-finished product including the metal texture layer by printing the metal ink containing metal particles uniformly dispersed therein on the base sheet, a unit for forming the printing layer on the transparent film, and a unit for layering the transparent film on the semi-finished product to produce a desired sheet, undesirably making it difficult to control the manufacturing process and causing problems such as increased manufacturing cost and lowered productivity.
Also, because the metal particles contained in the metal ink cause the metal texture to be exhibited, inherent properties and texture of only the metal cannot naturally manifest themselves, undesirably degrading product value.
The present inventors carried out earnest work to solve the problems encountered in the related art and thus have discovered that a thin stainless steel sheet in which various surface processing treatments may be performed and which is lightweight and has superior corrosion resistance, wear resistance, heat resistance, fire resistance, processability and durability is preferably used as the decorative metal sheet.
However, typical thin stainless steel sheets, having a monotonous cold metal texture and being glossy, are unsuitable for use as a decorative surface finish.
Hence, provided as the decorative metal sheet is a thin stainless steel sheet subjected to matte surface treatment and having various colors and a thickness of about 0.05˜0.15 mm.
Generally, a thin stainless steel sheet having a thickness of about 0.8˜1.5 mm which was mainly subjected to matte surface treatment through a physical process using hairline brush, bead blast, vibration brush and so on is useful. However, in the case where a thin stainless steel sheet having a thickness of about 0.05˜0.15 mm suitable for use as the decorative metal sheet is subjected to matte surface treatment using the above physical process, its surface may be undesirably damaged.
Also, when the surface of the thin stainless steel sheet which is glossy is subjected to inorganic coating using a nanoceramic (SiO2, SnO2, etc.) or ionic coating with titanium (Ti), chromium (Cr), zirconium (Zr) or the like using PVD, the surface roughness thereof may be reduced and a variety of colors may be obtained.
Furthermore, nanoceramic coating is performed by coating a nano material having a size of 10˜20 nm using a spraying process and thus results in lower manufacturing cost than when using PVD, and also enables the use of an organic dye or a nano inorganic dye thus obtaining a wider variety of colors.
On the other hand, when ionic coating is performed using PVD, a material such as Ti, Cr, Zr or the like evaporates and its minute particles are applied on the surface of the stainless steel sheet in a high vacuum, thus achieving superior quality but undesirably causing higher manufacturing cost, compared to a wet process. The color thereof may be gold, bronze, black, etc., depending on the kind of gas injected when coating.
The nanoceramic coating which results in a coating thickness of about 20 μm or less or the PVD inorganic coating which results in a coating thickness of about 0.5˜1.0 μm causes almost no damage to the coating layer upon post-processing such as bending or embossing, thus exhibiting a surface roughness and colors required of surface finishes of a variety of products.
According to tests by the present inventors, although the thin stainless steel sheet having a thickness of about 0.05˜0.15 mm and subjected to nanoceramic coating or PVD ionic coating has no cushioning and thus may be processed to have an embossed pattern using an emboss roll composed of a positive pattern roll and a negative pattern roll corresponding thereto, it is difficult to exhibit an elaborate fine clear pattern, and also the use of the emboss roll composed of the positive pattern roll and the negative pattern roll makes the processing difficult, increases the manufacturing cost, and incurs a great amount of wear, undesirably resulting in a short service life.
Furthermore, even when the above thin stainless steel sheet is embossed to form the embossed pattern, it is poor in terms of scratch resistance, shape stability, flexibility and wrinkling resistance, and a smooth cut surface cannot be obtained when it is cut and it is difficult to package, handle and construct.